The Model 281 Proteus and Model 401 Sierra were exhibited statically at Nellis Air Force Base during Aviation Nation 2025.
The Nellis Air Force Base in Nevada held the Aviation Nation 2025 air show from April 5th to 6th, 2025. Along with aerial demonstrations, numerous airplanes were exhibited statically. Included among them were two unusual planes: the Model 281 Proteus and a Model 401 Sierra. Scaled Composites .
Proteus and the 401s have been carrying out immensely significant tasks for several years now, and they still do so presently," stated Greg Morris, President of Scaled Composites. "It’s a privilege for us to temporarily pause their flight testing programs to allow the public to see these airplanes.
This marked a crucial moment for one particular aircraft since it was the initial instance when this occurred. Model 401 Sierra was exhibited publicly. Our friend Steve Fortson was one of the attendees at the airshow and took the photographs featured in this article, offering us an up-close view of these two intriguing airplanes.
Model 281 Proteus
The Model 281 Proteus was created for extended stays at high altitudes, accomplished through the incorporation of dual elongated wings placed sequentially and minimal wing loading, along with two engines. Williams International FJ44-2E engines Specifically, Proteus was created to transport payloads weighing around 2,000 pounds to heights exceeding 50,000 feet and stay aloft for as long as 14 hours.
As a result, Scaled Composites characterizes Proteus as the globe’s most economically efficient high-altitude research airplane. The missions assigned to Proteus encompass telecommunication services, surveillance activities, scientific studies of the atmosphere, commercial image capturing, and support for space launches.
The aircraft operates in an optional pilot mode; the company characterizes it as suitable for both manned flights and drone operations. Typically, it requires a crew of two pilots during operation, but it has the capability to perform semi-autonomous flights or be managed remotely from a ground control station when functioning without onboard personnel.
The Model 281 made its maiden flight in 1998 and has since carried more than 35 distinct payloads. It continues to serve as a valuable resource for the high-altitude research sector, having completed over 1,000 missions totaling approximately 4,500 flight hours up until now. In the year 2000, Proteus set three global altitude benchmarks that remain unbroken: Highest Level Flight Altitude at 62,385 feet, Absolute Service Ceiling of 63,245 feet, and Maximum Height Carrying a 1,000 Kilogram Load at 55,994 feet.
The airplane showcased at Nellis The sole Model 281 ever constructed featured some intriguing markings on its side. Notably, one marking signified a snake bite incident occurring during landing, whereas another denoted an unexpected activation of the sprinkler system in Proteus’ hangar while the plane was inside.
Model 401 Sierra
The Model 401 Sierra initiative was conceived as an entirely new approach aimed at showcasing affordable manufacturing techniques through a prototype aircraft designed for solo piloting, propelled by a singular turbofan engine, and functioning within mid-level altitudes. Two such identical crafts were constructed. The development process spanned just twenty-four months from inception to the maiden voyage of the inaugural Model 401 in October 2017; half a year after this event, the second airplane also took to the skies.
As a nod to Scaled Composites' previous work Agile Responsive Effective Support (ARES) During testing, the two Model 401 jets have earned the moniker “Sons of Ares,” with Ares being the deity of warfare in Greek mythology. Consequently, these planes have acquired additional nicknames: Phobos and Deimos, representing the deities of dread and panic, correspondingly. These names are echoed in their registration numbers; N401XP for one and N401XD for the other.
The Model 401, referred to internally at the company as Sierra, stands out as one of the most enigmatic planes presently undergoing test flights beyond military confines. After expanding their operational capabilities, these aircraft began engaging in payload tests aimed at meeting the needs of numerous clients across different sectors.
Indeed, according to Scaled Composites, the aircraft can accommodate various types of payloads, boasting more than 80 cubic feet of internal payload space and capable of carrying up to 2,000 pounds of load. These payloads could include a variety of systems. laser directed energy system , as observed in 2022 with a pod mounted underneath the fuselage adorned with artwork apparently alluding to a laser.
We shouldn't dismiss the potential for test flights aimed at developing new methods to safeguard aircraft from directed energy weapons. Keep in mind that a Model 401 was the initial aircraft observed sporting a mirror-like finish about two years prior. This type of coating later surfaced on F-22s, F-35As, F-35Cs, as well as F-117s collaborating with U.S. Air Force and Navy testing and assessment teams.
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